The long-range objectives of this program project are the identification, characterization, and validation of distinct subtypes or dimensions of reading disability. To accomplish these objectives during budget periods 10-14, a test battery that includes measures of cognitive abilities and of reading and language processes will be administered to a total of 1,000 subjects, including identical and fraternal twin pairs in which at least one twin is reading disable, parents of these twins, members of identical and fraternal twin families in which the children are normal readers, and nontwin reading-disabled and control children for whom extensive longitudinal data have been collected. Resulting twin and family data will be used to validate alternative typologies and to conduct genetic analyses. A survey of immune disorders and laterality will also be undertaken in the twin sample, and subsets will be evaluated for immunology and neuroanatomical differences using autoantibody assays and magnetic resonance imaging. A group of identical twins will also be administered differential training in phonological coding to assess subtype-by-treatment interaction. Concurrently, a linkage analysis will be employed to test the hypothesis that a form of reading disability is due to an autosomal dominant gene located on chromosome 15.